The objectives of the Clinical Core are: 1. to provide a central laboratory for recruitment and characterization and asthmatic subjects; 2. performance and quality control of pulmonary function testing, antigen skin testing, and methacholine and allergen inhalation testing; 3. perform bronchoscopy with bronchoalveolar lavage and endobronchial biopsy; 4. coordinate database development; and 5. facilitate interproject communication. In doing so, the clinical aspects of the Program Project grant will function at a high standard.